Here's something that may help.
Note the difference between regret and guilt. Regret can motivate us; regret does no positive good, but only paralises us.
Three Steps to Genuine Change - High Holidays with Aish
Confession, healthy regret, and resolution to change. That's how I forgive myself.
I hope you find something worthwhile out of this. I saw your post, and had just read this earlier this morning. Naturally, I thought of it for you right away.
Shalom!